This invention is intended primarily to provide an air filtering unit suitable for commercial institutions, where it is important to move substantial amounts of air which is filtered thoroughly by a plurality of filtering elements designed to accomplish a variety of filtering functions.
There are, of course, various filtering systems in which a plurality of separate filtering units are installed in a series arrangement. Such units may include an electrostatic filtering element, polyurethane foam elements, carbon filters for odor absorption, etc. In most of the known arrangements, the separate types of filter elements are separately installed in and removed from the air filtering system. There are, in the prior art, disclosures of a single filter element incorporating more than one type of filtering material layer; so that replacement of such a filtering unit does replace more than one type of filtering material. However, the known constructions do not provide a filtering cassette of the type disclosed herein, which has an outstanding combination of advantages, including the following:
1. Compactness, PA1 2. Containment of dirt, PA1 3. Ease of servicing, PA1 4. Flexibility in changing component elements, PA1 5. Structural rigidity, PA1 6. Protection of delicate parts, PA1 7. Ease of assembly and disassembly for cleaning, PA1 8. Improved grounding of the electrostatic elements, PA1 9. Simple arrangement for locking in the filter elements.
The aspects of this invention which provide the listed advantages will be made apparent as the disclosure proceeds.